Map Information
ABOUT THIS ISOCHRONE MAP
Travel time to an emergency is an important factor in deciding where to locate fire departments within counties. The ideal response time for a fire department to an emergency is within 4 minutes in large metro areas -- however, the travel time usually increases in more rural communities (National Fire Data Center).
This map aims to show the area that a fire department can travel to within 4 minutes, 6 minutes, 8 minutes and 10 minutes in Calaveras County, a county that has already seen large fires and emergencies in 2024.
The population within each Census Block Group of the county is also given. The combination of drive times and population data can hopefully highlight areas that are underserved, or where an additional firehouse would increase coverage.
ABOUT THE DATA AND METHODS
Network Data and Analysis The OSMnx open-source library was used to conduct the network analysis by using OpenStreetMaps to query CA county spatial data and construct node graphs of the county of interest. Edge speeds and travel times within the node graph of the county were also calculated using OSMnx.
Census Data: Data was fetched via an API request to the American Community Survey endpoint -- the block group dataset was queried to maintain a high level of granularity.
Calculation of Population within Travel Times: To estimate the population within the travel times, the area for each block group was calculated. Next, all isochrone geometries were combined to form a single geometry. The area of intersection of the isochrone geometry and each block group was then calculated. To estimate the population within the travel time for each block group, the ratio is multiplied by Total Population
Fire Station Data: The fire station location data may be outdated or not current and is not necessarily a complete list of fire stations in California.